}
    $LOCAL_HOST= lc($LOCAL_HOST) ;

    # If no $DOCUMENT_ROOT, try to guess it from $HOME, username, $USER_DIR.
    unless (length($DOCUMENT_ROOT)) {
        my($home) ;
        unless ($home= $ENV{'HOME'}) {
            my($uname)= getpwuid($<) || $ENV{'USER'} || `whoami` || `id -un` ;
            chomp($uname) ;
            &read_home_dirs unless %home_dir ;   # only read when needed
            $home= $home_dir{$uname} ;
        }
        $DOCUMENT_ROOT= "$home/$USER_DIR" ;

        die "Could not determine DOCUMENT_ROOT; edit the $0 script to set it.\n"
            unless (-d $DOCUMENT_ROOT) ;

        print STDERR "DOCUMENT_ROOT set to \"$DOCUMENT_ROOT\"\n" ;
    }
    $DOCUMENT_ROOT=~ s#/$## ;

    # Allows &filename_to_url() to unalias as best as possible.  Note that 
    #   use of &filename_to_url() can be avoided by the user; see note in 
    #   that routine.
    %UN_ALIAS= (reverse (%ALIAS, %SCRIPT_ALIAS) ) ;

    # These are to compare equivalency to later, in &filename_to_url().
    ($DOC_ROOT_DEV, $DOC_ROOT_INODE)= stat("$DOCUMENT_ROOT/.") ;
    
    $DOC_ROOT_EXISTS= -e _ ;
    
    # Set CWD from shell variable, else from `pwd`.
    $CWD= $ENV{'PWD'} || `pwd` || die "couldn't run pwd: $!" ;
    chomp($CWD) ;


    # These are used by &extract_urls().
    # This is a complete list of URL-type attributes defined in HTML 4.0,
    #   plus any others I found, like nonstandard ones or from an earlier HTML.
    # Only a few of these are commonly used, as of early 1998.
    # The set in %html_urls could possibly link to HTML resources, while the
    #   set in %non_html_urls could not.  The %special(.*) sets, here for 
    #   reference only, include URL attributes that require special handling.

    %html_urls= ( 'a'          => [ 'href' ],
                  'area'       => [ 'href' ],
                  'frame'      => [ 'src', 'longdesc' ],
                  'link'       => [ 'href', 'urn' ],
                  'img'        => [ 'longdesc', 'usemap' ],
                  'q'          => [ 'cite' ],
                  'blockquote' => [ 'cite' ],
                  'ins'        => [ 'cite' ],
                  'del'        => [ 'cite' ],
                  'object'     => [ 'usemap' ],
                  'input'      => [ 'usemap' ],
                  'iframe'     => [ 'src', 'longdesc' ],
		  'ilayer'     => [ 'src' ],
		  'layer'      => [ 'src' ],
		  'fig'        => [ 'imagemap' ],
		  'overlay'    => [ 'imagemap' ],
		  'meta'       => [ 'url' ],
		  'note'       => [ 'src' ],
                ) ;

    %non_html_urls= ( 'body'    => [ 'background' ], 
                      'img'     => [ 'src', 'lowsrc', 'dynsrc' ],
                      'input'   => [ 'src' ],
                      'script'  => [ 'src', 'for' ],

		      'fig'     => [ 'src' ],
		      'overlay' => [ 'src' ],
		      'select'  => [ 'src' ],
		      'ul'      => [ 'src' ],
		      'h1'      => [ 'src' ],
		      'h2'      => [ 'src' ],
		      'h3'      => [ 'src' ],
		      'h4'      => [ 'src' ],
		      'h5'      => [ 'src' ],
		      'h6'      => [ 'src' ],
		      'hr'      => [ 'src' ],
		      'table'   => [ 'src' ],
		      'td'      => [ 'src' ],
		      'th'      => [ 'src' ],
		      'tr'      => [ 'src' ],

		      'bgsound' => [ 'src' ],
		      'embed'   => [ 'src' ],
                  ) ;

    # %special_urls= ( 'base' => [ 'href' ] ) ;
    #
    # %special_html_urls= ( 'object' => [ 'codebase', 'data' ] ) ;
    #
    # %special_non_html_urls=
    #      ( 'head'   => [ 'profile' ],
    #        'object' => [ 'codebase', 'archive', 'classid' ],
    #        'applet' => [ 'codebase', 'code', 'object', 'archive' ],
    #        'form'   => [ 'action', 'script' ]
    #      ) ;